The last American niobium mine closed in 1959, and all U.S. niobium is now imported from other countries. This is:
A. bad for the United States because the U.S. must give money to other countries in order to obtain niobium.
B. bad for the United States because the niobium miners were put out of work.
C. good for the United States because the resources used to mine niobium are freed to do something for which the U.S. has a comparative advantage.
D. good for the United States because it is always better to import raw materials from other countries, and export finished goods.